Photoluminescence from ZnO nanowires

Abstract

Self-organized ZnO nanowires were grown by metal-organic chemical vapor deposition on sapphire substrate. Steady-state photoluminescence (PL) from the samples with different densities of the nanowires was studied in wide range of temperatures and excitation intensities. At 13K the PL spectrum consisted of sharp exciton lines at 3.354, 3.357, and 3.363eV and a weak red band with a maximum at ∼1.75eV. The peak intensity of the red band was four orders of magnitude lower than that of the strongest exciton line. The authors investigated also the effect of ambient on PL at room temperature. In vacuum the PL intensity increased linearly with the excitation power density in the range from 3×10−4to0.3W∕cm2, whereas in air the PL intensity increased superlinearly. Such behavior is attributed to photoinduced adsorption of species from air which increases the near-surface barrier and depletion region.